This invention relates to pressure or force sensing transducers, and more particularly to capacitive pressure or force sensing transducers.
There are many forms of pressure sensing transducers in the prior art which utilize capacitive sensors. As set forth in copending application Ser. No. 671,612, filed Mar. 29, 1976 U.S. Pat. No. 4,084,438 issued Apr. 18, 1978 the present inventor and Dennis K. Briefer, such transducers typically include a metal housing with a metallic diaphragm and are subject to the shortcomings set forth in that application. Capacitive pressure sensing transducers have also been made utilizing quartz or other dielectric materials for capsules with conductive films on the interior surfaces. West German patent application No. 2,021,479 and Polye, U.S. Pat. Nos. 3,715,638 and 3,858,097, are illustrative of such constructions. The operative portions of these prior art constructions are substantially flat and of substantially uniform thickness. With such uniform thickness there is a stress concentration in the region where the material is fused or cemented together and the deflection of the conductive surfaces of the transducer varies with the radial position of the deflected portion.
Accordingly, it is an object of the present invention to provide a capacitive pressure transducer whose deflection and maximum stress is controlled by the elastic properties and strength of the dielectric plate material rather than by the properties of the fusing or cementing material.
Another object is to provide a capacitive pressure transducer whose capacitive portions remain substantially parallel throughout its operating range.
A further object is to provide a capacitive pressure transducer with increased internal volume.